In developing countries, the levels of quinolone resistance among gram-negative bacteria are very low, probably because of the low use of these antimicrobial agents, in association with their high cost. One of the most fundamental measures that could be taken to minimize quinolone resistance and antibiotic resistance in general is to eliminate supplementation of animal feeds with antibiotics, including tetracycline, macrolide, and quinolone derivatives. Escherichia coli is likely the Enterobacteriaceae in which the increase in quinolone resistance has been most evident. This trend in fluoroquinolone resistance has also been shown in Enterobacteriaceae from bacteremias from hospitals in England and Wales. Pseudomonas aeruginosa and Acinetobacter baumannii are the two most relevant nonfermentative gram-negative bacteria. They share similar characteristics, one being the ability to develop resistance to multiple antimicrobial agents. Quinolone resistance in enterococci has developed rapidly, and there are high rates of resistance, especially among vancomycin-resistant enterococci. In 1998, plasmid-mediated resistance in Klebsiella pneumoniae, caused by the qnrA gene, was reported. The future of the increase of quinolone resistance is difficult to predict, but it will clearly continue to increase unless steps are taken to reduce it, such as the development of SOS inhibitors.

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45. Sierra,J. M.,, F.Marco,, J.Ruiz,, M. T.Jimenez de Anta, and, J.Vila.2002. Correlation between the activity of different fluoro-quinolones and the presence of mechanisms of quinolone resistance in epidemiologically related and unrelated strains of methicillin-susceptible and -resistant Staphylococcus aureus.Clin. Microbiol. Infect.8:781–790.